Table REF  indicates that for the sample of 854 pulsars, some 60% of them have PA swings which appear RVM-like and 40% do not. What are the differences between these two classes? Figure REF  shows the distribution of \(\dot{E}\)  for the entire sample, the RVM class, the flat class and non-RVM class. It can be seen that the RVM class has a distribution almost identical to that of the total sample whereas the flat class of pulsars is biased towards high \(\dot{E}\)  and the non-RVM pulsars show a bias towards low values of \(\dot{E}\) . Indeed only 8 out of 77 pulsars with \(\dot{E} > 10^{34.5}\)  erg s\(^{-1}\)  are in the non-RVM class. In many ways this is not a surprise. Pulsars with high \(\dot{E}\)  have previously been shown to have `simpler' profiles with high degrees of linear polarization and unbroken PA swings [1]}, [2]}. This may arise because their emission heights are relatively high [3]} thus minimising the distortion of the polarization properties on the traverse through the magnetosphere. In contrast, the pulsars with low \(\dot{E}\)  often have profiles which are a blend of multiple components (see Figure REF ), possibly arising over a large range of emission heights, thereby distorting the PA swing (e.g. [4]}, [5]}).
